Method of lubricating surfaces with a vaporous lubricant



oxygen and nitrogen, as well as oxygen per se.

United States Patent METHOD OF LUBRICATING SURFACES WITH A VAPOROUS LUBRECANT Stanley S. Sorem, Orinda, and Charles H. Bailey, Berkeley, Calif., assignors to Shell Oil Company, a corporation of Delaware No Drawing. Filed Sept. 11, 1956, Ser. No. 609,087

6 Claims. (Cl. 184-1) This invention relates to lubricating compositions suitable for use in high temperature and high speed operations.. More particularly, it pertains to the lubrication of bearing surfaces in aircraft gas turbine engnes, and the like, with a vaporous lubricating composition.

The inadequacy of liquid lubricants to function effectively, and lubricate aircraft engines, such as turbo jet and turbo prop engines operating at high temperatures and at high-speeds is well recognized. See, for example, Sorem et al. High-Temperature Bearing Operation in the Absence of Liquid Lubricants, in the July-August 1956 issue of Lubrication Engineering; also the June 1955 article entitled High Temperature-High Speed Aircraft Turbines Seek New Lubricants and Bearings in the Society of Automotive Engineering Journal and Muellers article entitled Air Lubricated Bearings in Product Engineering for August 1951.

It has now been found that unexpectedly superior lubrication can be provided for metal surfaces subjected to high temperatures and high speeds by contacting the surfaces to be lubricated with a vaporous mixture comprising a substantial or major proportion of air or another free-oxygen-containing gaseous material, and a lesser amount or proportion of a vaporized petroleum resinous fraction derived from a liquid hydrocarbon having an end boiling point of about 600 F. and preferably not greater than 550 F. If desired, the petroleum resin can be added in small amounts of from 0.1% to to the same liquid hydrocarbon from which it is derived or to a different liqu.d hydrocarbon and the liquid hydrocarbonpetroleum resin mixture used in combination with air in a vaporous state as the lubricant. For the most effective results the air or the like to hydrocarbon (petroleum resin or hydrocarbon contains added petroleum resin) should be in the weight ratio of from about 7:1 to about 10:1, respectively.

Below the ratio of 7:1 carbon formation of the airhydrocarbon mixture at high temperatures has been found to occur excessively, While above the ratio of 10:1 there are tendencies of the mixture to cause oxidation of bearings which oxidaton products in turn rorm abrasives at high tern eratures.

Instead of air, other free-oxygen-containiug gaseous materials can be used, such as other mixtures of free in such a case the ratio of the oxygen to hydrocarbon should be ice adjusted accordingly so that the ratio of free oxygen to hydrocarbon is equivalent to that of the free oxygen to hydrocarbon in the air-hydrocarbon mixtures specified above. Thus, expressed in terms of free oxygen, the weight ratio of oxygen to hydrocarbon is from about 7:5 to aboutZ: 1, respectively.

The petroleum resins suitable for use as an essential (although minor) component of the vaporous lubricant of this invention can be obtained by any suitable means such as for example, by fractionally distilling light petroleum products such as naphthas, kerosene, or IP-1, J P-2, J.P3 or iP-4 fuels, 1005, 1010 or 1065 lube oils into cuts or fractions. The distillate (from above fraction) cuts having an end boiling point of around 300-400 F. are discarded and the bottoms or residue fraction is clay and/ or solvent treated to recover a petroleum resinous material thereof which resins contain polar compounds, e.g. of sulfur, oxygen and nitrogen-containing organic compounds. This polar rich petroleum resip is used in its vaporous state as a component of the vaporous lubricants of this invention.

For example, a suitable starting petroleum product from which the desired petroleum resins can be obtained is a lP4 fuel, the properties of which are given on page 5, Table 1, of the specification. This fuel is fractionated by distillation into (a) light ends, (b) intermediate cut and (c) bottoms. Each of these three fractlons (a), (b) and (c) had the following properties: (a) Light ends The bottoms fraction (0) is percolated through a bed of syn hetic magnesium silicate (Florisil) and the petroleum resins adsorbed on the gel are recovered by washing with a solvent. Specifically, the resins adsorbed on the gel are eluted with a small quantity of isopentane and then displaced by washing with a 50-50 mixture of ben- Zone and isopropyl alcohol. The resins are recovered from the 50-50 mixture of benzene and isopropyl alcohol by distillation. On analysis, petroleum resin (X) thus recovered contained about 6.25% by weight of total sulfur, 10.8% by weight of total oxygen, 0.02% by Weight of total nitrogen and the balance being predominantly alkylene and alkyl substituted mono and polyaromatics. The sulfur compounds in the resin include sulfides, thiophenes, mercaptans and derivatives thereof; the oxygen compounds include phenolic and organic carboxylic acids, while the nitrogen compounds include such materials as toluidine, quinoline, collidine and the lIke. The petroleum resin can be added in an amountv of from 0.1% to 5% by weight to a light lubricant such as kerosene, 1005, 1010 or 1065 lubricating oil, or a JP-4 fuel and this mixture can be adm.xed with the air or the like, preferably in the ratio of 1:7 to :1, respectively and used as a lubricant. Such a lubricant can be obtained by forming a mixture of petroleum resin (X) with J P4 fuel, or with a 1005 or 1010 lube oil and blending this mixture with air in the ratio of 1:8, respectively. The properties of a JP4 fuel and 1005, 1010 and/or 1065 lube oils are as follows:

TABLE I Properties of JP4 fuel Gravity, API 98.3. Color 0. RVP,'lb. at 100? F. 2.0. Corrosion, Cu strip (Air Well) Pass. Water tolerance Immiscible. Sulfur, percent w.' .248. Aromatics, percent vol. 12.1. Olefins 1.5% v. Saturates 86.9%.

ASTM DISTILLATION. F. IBP 141 FBP 466 10% Evap., F. 226 50% Evap., F. 346 90% Evap., F. 423 Percent rec. 98.0 Percent res. 1.0 Percent loss 1.0

Properties of gas turbine lube oils Grade mm 1010 1065 Flash, 000, F 225 300 465 Pour, F 7 70 0 Viscosity, SUS at 100 F s Cs. at 100..-- 59.4 530 Neutral No 0.1 max 0.02 0.01 Ash None None None In Table II, the JP-4 fuel as well as the 1005, 1010 and 1065 gas turbine lube oils (Table I) will be referred to by the letters A, B, C, and D, respectively.

Still further improvement can be obtained by providing the bearing surfaces with a compound capable of coating or reacting with said surfaces and containing at least one other element which exhibits acidic chemical properties, particularly the chemically acidic elements of groups V to VII of the periodic table. Those elements which are particularly effective for this purpose are phosporus, sulfur, selenium and tellurium, occuring in the right hand side of groups V and VI. The surface compound can be provided in a separate and distinct operation, as by a pretreatment with a suitable active agent of the acidic element, and/or in the same operation of lubrication as by incorporating the agent in the vaporous lubricating mixture.

The surface compounds appear to serve at least two functions, both advantageous to the effective lubrication. They provide a load carrying film, such as a metal phosphide or phosphate or a metal sulfide, and they are effective in minimizing the undesirable production of carbonaceous deposits, presumably in part by shielding the lubricating vaporous mixture at the elevated temperature from the catalytic actvity of the metal of the bearing.

When the surfaces to be lubricated are chemically pretreated, they can be so treated by various methods which are well known in the art.

. The chemically reactive agents capable of forming protective films on the contacting metallic surfaces can be normally gaseous, liquid or solid and they may be utilized in the gaseous, liquid or solid state. Materials which are readily utilized in the gaseous state include fumes of sulfur, hydrogen sulfide, carbon disulfide, chlorine, etc. The sulfide or chloride film can be formed on the surface to be protected by simply contacting the gas with the hot metal surface to be protected. In cases 4 where reagents are used in the liquid state the metal surface can be dipped in, sprayed with, or painted with an aqueous or non-aqueous composition containing the reactive agent. Illustrative compositions are aqueous solutions of hydrogen sulfide, ammonium sulfide, ammonium polysulfide, sodium polyselenide, etc. The compositions can be a colloidal aqueous, or oil suspension of sulfur, sulfurized oils, such as sulfurized lard oil, or mineral oil containing sulfurized lard oil and/or sulfur, dialkyl selenides, e.g., dilauryl selenide, and the like. Phosphate films can be formed on the metal surface by treating the metal surface with an aqueous solution containing phosphoric acid or a phosphate salt, e.g., tribasic sodium phosphate, or mixtures thereof. The metal surface can also be dusted with a solid agent, such as sulfur flowers and thereafter heated so as to form a sulfide film on the metal surface. Other methods of pretreating the surface desired to be lubricated include the heating of the metal in a mineral lubricating oil containing; (a) an organic acid phosphate or phosphite, such as an aryl or alkyl acid phosphate, e.g., triethylphosphate, diphenyl phosphoric acid, dilauryl phosphoric acid, or an alkyl phosphite, such as tributyl phosphite, and/or (b) a halogenated hydrocarbon or halogenated organic compound such as a chlorinatedolefin, trichlorophosphonates, CCL fiuorinated oefins, trifiuoroacetic acid and mixtures thereof, a chlorinated aryl compound such as a chlorinated naphthalene, a chlorinated anthracene, a chlorinated alkylbenzene, dichlorodibenzyl disulfide, pentachlorophenol, etc. Still other methods of forming anti-scufling, anti-seizing and wear resistant films on surfaces to be lubricated are described in Metal Coloring by 'Hiorns; McMillian Company of London. A preferred method of forming protective films is to run the assembled machine at a temperature of about 400 F. while lubricating with a lubricant containing the desired pretreating additive such as sulfurized mineral oil containing about 1% sulfur.

To compositions of this invention can be added conventional anti-oxidants such as p-N-butylamino-phenol, N,N-di-sec-butyl-p-phenylenediamine, butylated 4-metl1- oxy phenol, 2,fi-di-tert-butyl-p-cresol, 2,2'-rnethylene-bit- (G-tert-butyl-p-cresol); dispersants of the polymer ester type, oiliness agents of the fatty acid type, e.g., oleic and stearic acids; mild-extreme pressure agents of the sulfurphosphorus type and the like.

The surface treating compounds or anti-scufiing agents, which are capable of forming protective films on the surfaces to be lubricated can be introduced into the air or oxygen vaporous petroleum resin lubricant containing blend in amounts of from 0.01% to 5% and prefferably from 0.1% to 1% so that the protective film can be formed in situ. The air-petroleum resin containing lubricant blend, with or without the anti-scufiing forming agents, can be sprayed or atomized onto the surface to be lubricated such as gears and bearings so that the entire surface is enveloped or blanketed in a vaporous lubricant. Also, the lubricant may be vaporized into the air stream at any convenient location and the mixture conducted to the surface to be lubricated.

The air-petroleum resin containing lubricant blend can be used as a conventional mist lubricant during the periods of operation when machine parts are at temperatures beiow the end boiling point of the lubricant.

In order to demonstrate the effectiveness of vaporous lubricants of this invention at elevated temperatures and high speeds, a high-speed bearing assembly as shown in Figure 2 of Sorem et al. paper referred to above was TABLE II.TEST RESULTS Composition Time of Bearing Failure 1. Dry 1 min. 2. Air-lubricant B blend in 7:1 ratio, 4-5 hours, failed due to carbon respectively. deposits. 3. Air-lubricant C blend in 7:1 ratio, Do.

respectively. 4. Air-fuizlA blend in32z1 ratio, respec- 3 hours, failed due to abrasion.

tive y. 5. Air-fuel A blend in 30:1 ratio, re- Do.

spectively, and in presence of CS 6. Air-lubricant B blend in 4:1 ratio 5-6 hours, failed due to carbon respectively. deposits. 7. Air-fuel A blend in 4:1 ratio, re- Do.

spectively. 8. Air-fuel A blend in 14:1 ratio, re- 5-6 hours, failed due to abraspectively. sion. 9. Composition 7 containing 1.25% 5-6 hours, failed due to carbon triethyl phosphate. deposit. 10. Composition 8 containing 1.25% tn- 5-6 hours failed due to abrasion.

ethyl phosphate. 11. Air-fuel A blend in 7 :1 ratio respec- 10hours, hearings in good conditi ely. tion,testst0ppcd. 12. Air-fuel A blend in 10:1 ratio, re- Do.

spectively. 13. Light ends (a) Table I 2min.,bearing seized. 14. Intermediate cut (b) Table I l0honrs, bearingseized. 15. Bottoms (0) Table I, resins 7 hours, surface warm and removed. roug 16. Air-petroleum resin (X) m8:1rat10- 22 hours, bearing m excellent condition. 17. Air-fuel A blend containing 0.4% Do.

petroleum resin (X) in 8:1 ratio. 18. Air-Intermediate cut (b) containing Do.

0.4% petroleum resin (X) in 8:1 ratio. 19. Air-Bottoms (0) containing 0.4% Do.

petroleum resin (X) in 8:1 ratio. D

20. Composition 17 +0.66% wt. tris (isopropyl) phosphite.

Lubricants of this invention are particularly applicable for ball and roller bearings of gas turbine engines where operating temperatures are high and can also be used for lubrication of various other machines and equipment operating at high temperatures and speeds. Lubricating by the method of this invention can be modified to meet other high temperature requirements and can be applied to any mechanisms operating at high temperature speeds and loads such as conveyor belts, furnace belts and the like.

We claim as our invention:

1. A process of lubricating solid surfaces subjected to elevated temperatures which comprises contacting said surfaces with a vaporous lubricant consisting essentially of a blend of free-oxygen-containing gaseous material and a vaporized petroleum resin in the weight ratio of from 7:1 to 10:1, respectively.

2. The process of claim 1 wherein the free-oxygencontaining gaseous material is air and the petroleum resin is derived from the bottoms of a liquid petroleum fraction having an end boiling point of about 600 F. and said petroleum resin consisting essentially of a mixture of sulfur, nitrogen, and oxygen containing organic compounds and the balance being aromatic hydrocarbon which are naturally present in such a liquid petroleum fraction in the weight ratio of from 7:1 to 10:1, respectively.

3. A process of lubricating engines operating at elevated temperatures which comprises contacting parts to be lubricated with a blend of air and a liquid petroleum fuel having an end boiling point of about 600 F., said fuel containing from 0.1% to 2% of a petroleum resin consisting predominantly of natural occurring sulfur, oxygen and nitrogen organic compounds and the balance being a mixture of monoaromatic hydrocarbons and polyaromatic hydrocarbons; said blend of air and petroleum mixture being in the weight ratio of from 7:1 to 10:1 respectively.

4. The process of claim 3 wherein the vaporous lubricant blend contains from about 0.01% to 5% of trialkyl phosphite.

5. A process of lubricating engines operating at elevated temperatures which comprises preforming on the parts requiring lubrication a phosphate film thereon by operating the engine with a lubricating oil containing from 0.01% to 5% of a reactive organic phosphorus compound of the group consisting of trialkyl phosphates, dialkyl hydrogen phosphates, diaryl hydrogen phosphates, trialkyl phosphites, dialkyl hydrogen phosphites and diaryl hydrogen phosphites at an elevated temperature until a P-containing film forms and thereafter under engine operating conditions blanketing said parts with a vaporous lubricant comprising a blend of air and a petroleum fuel having an end boiling point of about 600 F. containing from 0.1% to 2% of a petroleum resin consisting predominantly of natural occurring sulfur, oxygen and nitrogen organic compounds and the balance being a mixture of monoaromatic hydrocarbons and polyaromatic hydrocarbons, said blend of air and petroleum mixture being in the weight ratio of from 7:1 to 10:1 respectively.

6. A process of lubricating engines subjected to high temperature, high speed which comprises blanketing the parts to be lubricated with a vaporous lubricating composition consisting essentially of a blend of air and petroleum resin derived from the bottoms of a liquid petroleum fraction having an end boiling point of about 600 F., said resin consisting predominantly of natural occurring sulfur, oxygen and nitrogen organic compounds and the balance being mixtures of mono and poly aromatic hydrocarbons, said blend being in the weight ratio of from 7:1 to 10:1 respectively and from 0.01%5% of triisopropyl phosphite.

OTHER REFERENCES Boner: Lubricating Greases, Reinhold Pub. NY. (1954), page 799. 

1. A PROCESS OF LUBRICATING SOLID SURFACES SUBJECTED TO ELEVATED TEMPERATURES WHICH COMPRISES CONTACTING SAID SURFACES WITH A VAPOROUS LUBRICANT CONSISTING ESSENTIALLY OF A BLEND OF FREE-OXYGEN-CONTAINING GASEOUS MATERIAL AND A VAPORIZED PETROLEUM RESIN IN THE WEIGHT RATIO OF FROM 7:1 TO 10:1, RESPECTIVELY. 